Introduction to MycologyIntroduction to Mycology..

Over theOver the course of time, more than 100,000 course of time, more than 100,000 species of fungi have been recognized and species of fungi have been recognized and described. However, fewer than 500 of described. However, fewer than 500 of these species have been associated with these species have been associated with human disease. The remainders are only human disease. The remainders are only able to produce disease in hosts that are able to produce disease in hosts that are debilitated or immunocompromised.debilitated or immunocompromised.

What is mycology?What is mycology? MycologyMycology is the study of fungi. The is the study of fungi. The

disease caused by fungi is called disease caused by fungi is called MYCOSES.MYCOSES.

What are fungi?What are fungi? Eukaryotic, spore-bearing, heterotrophic Eukaryotic, spore-bearing, heterotrophic

organisms that produce extracellular organisms that produce extracellular enzymes and absorb their nutrition.enzymes and absorb their nutrition.

General information's about FUNGI:General information's about FUNGI: Fungi are not plants or animals, they form a Fungi are not plants or animals, they form a

separate group of higher organisms, distinct separate group of higher organisms, distinct from both plants and animals, which differ from from both plants and animals, which differ from other groups of organisms in several major other groups of organisms in several major respects:respects:

FirstFirst:: Fungal cells are encased within a rigid cell wall, Fungal cells are encased within a rigid cell wall,

mostly composed of chitin and glucan. These mostly composed of chitin and glucan. These features contrast with animals, which have no features contrast with animals, which have no cell walls, and plants, which have cellulose as cell walls, and plants, which have cellulose as the major cell wall component. the major cell wall component.

Second:Second: Fungi are heterotrophic. This means that they Fungi are heterotrophic. This means that they

are lacking in chlorophyll and cannot make their are lacking in chlorophyll and cannot make their organic food as plants can, through organic food as plants can, through photosynthesis. Fungi live embedded in a food photosynthesis. Fungi live embedded in a food source or medium, and obtain their nourishment source or medium, and obtain their nourishment by secreting enzymes for external digestion and by secreting enzymes for external digestion and by absorbing the nutrients that are released from by absorbing the nutrients that are released from the medium. the medium. Some live on humans e.g. the Some live on humans e.g. the cause ringworm infections. Some live on insects, cause ringworm infections. Some live on insects, or plants.or plants.

ThirdThird:: Fungi are simpler in structure than plants or Fungi are simpler in structure than plants or

animals. There is no division of cells into organs animals. There is no division of cells into organs or tissues. or tissues.

The basic structure of the fungiThe basic structure of the fungi:: The basic structural unit of fungi is either a chain of The basic structural unit of fungi is either a chain of

tubular, filament-like cells, termed a hypha or hyphae tubular, filament-like cells, termed a hypha or hyphae (plural) or an independent single cell. (plural) or an independent single cell.

The living body of a fungus is called a mycelium which The living body of a fungus is called a mycelium which is madeis made up of a branching network of filaments known up of a branching network of filaments known as hyphae.as hyphae.

Fungal cell differentiation is no less complicated than Fungal cell differentiation is no less complicated than is found in plants or animals, but it is different. Many is found in plants or animals, but it is different. Many fungal pathogens of humans and animals change their fungal pathogens of humans and animals change their growth form during the process of tissue invasion. growth form during the process of tissue invasion. These These dimorphic pathogensdimorphic pathogens usually change from a usually change from a multicellular hyphal form in the natural environment to multicellular hyphal form in the natural environment to a budding, single-celled form in tissue. a budding, single-celled form in tissue.

In most multicellular fungi the vegetative In most multicellular fungi the vegetative stage consists of a mass of branching stage consists of a mass of branching hyphae, termed a mycelium. Each hyphae, termed a mycelium. Each individual hypha has a rigid cell wallindividual hypha has a rigid cell wall

They are filamentous, gram positive and They are filamentous, gram positive and bear fruiting bodies called spores.bear fruiting bodies called spores.

Can exist as single cells or chains of Can exist as single cells or chains of cells.cells.

History of taxonomyHistory of taxonomy All organisms were classified to:All organisms were classified to:

– PlantsPlants– AnimalsAnimals

Fungi were classified with plants:Fungi were classified with plants:– Immobility Immobility

Cell wallCell wall

By the Development of the electron microscope By the Development of the electron microscope in 1995s, Fundamental differences between the in 1995s, Fundamental differences between the bacteria and fungus were discovered: bacteria and fungus were discovered:

Although in many ways fungi resemble bacteria Although in many ways fungi resemble bacteria (neither has chlorophyll), they are unlike bacteria (neither has chlorophyll), they are unlike bacteria in: in:

Composition of the cell walls. Composition of the cell walls. Reproducing through sporulation or spore formation.Reproducing through sporulation or spore formation.

So it was classified again into 5 Kingdoms:So it was classified again into 5 Kingdoms: Bacteria.Bacteria. Protista .Protista . AnimaliaAnimalia Fungi Fungi PlantPlant

Importance of the fungi:Importance of the fungi: Fungi are abundant in the human environment, Fungi are abundant in the human environment,

and canand can found every where.found every where. Most of them lead a saprophytic life, living on Most of them lead a saprophytic life, living on

dead matter (e.g. Mushrooms). dead matter (e.g. Mushrooms). Fungal infections are assuming a greater Fungal infections are assuming a greater

importance, why!!importance, why!! This because of their increasing incidence This because of their increasing incidence

among:among:– Transplant patientsTransplant patients– ImmunocompromisedImmunocompromised

- AIDS- AIDS

In the last 20 years extraordinary changes in In the last 20 years extraordinary changes in fungal infection pattern!!fungal infection pattern!!

New pathogens have emergedNew pathogens have emerged Increasing international travelIncreasing international travel use wrongly of antimicrobial agentsuse wrongly of antimicrobial agents

Helpful fungi: In every day lifeHelpful fungi: In every day life The common bread-mould is a fungus.The common bread-mould is a fungus. Mushrooms (a vegetarian fungal protein)Mushrooms (a vegetarian fungal protein) Saccharomyces cerevisiae is used to ferment Saccharomyces cerevisiae is used to ferment

sugar to produce alcoholsugar to produce alcohol We also use fungi to produce flavourings and We also use fungi to produce flavourings and

vitamins.vitamins. Fungi play an essential role in both the Nitrogen Fungi play an essential role in both the Nitrogen

and Carbon cycle by breaking down dead and Carbon cycle by breaking down dead organic material. organic material.

We get some important drugs from fungi such as We get some important drugs from fungi such as the antibiotic (penicillin and cyclosporine).the antibiotic (penicillin and cyclosporine).

Helpful fungi: In ResearchHelpful fungi: In Research:: Scientists use several fungi to investigate Scientists use several fungi to investigate

basic functions that occur in all cells basic functions that occur in all cells because they are:because they are:

Simple Simple Easy to growEasy to grow Some cancer research is done using fungi Some cancer research is done using fungi

Why studying medical mycology is important?Why studying medical mycology is important?1.1. In humans, fungi cause skin infections such as In humans, fungi cause skin infections such as

ringworm and athlete's foot.ringworm and athlete's foot.2.2. They also cause several deadly diseases which They also cause several deadly diseases which

can be hard to treat.can be hard to treat.3.3. Most patients with deadly fungal diseases do Most patients with deadly fungal diseases do

not have a fully functional immune system. not have a fully functional immune system. – Leukaemia Leukaemia – AIDSAIDS– Drugs to suppress their immune system because of Drugs to suppress their immune system because of

organ transplantation.organ transplantation. 4- Antifungal drugs are often toxic.4- Antifungal drugs are often toxic. 5- There is a desperate need for new and 5- There is a desperate need for new and

better anti-fungal agents. better anti-fungal agents.

Some basic terms:Some basic terms: Fungi (fungus)Fungi (fungus) Hyphae (hypha) = cellular threadHyphae (hypha) = cellular thread Septate = hyphae with cross wallsSeptate = hyphae with cross walls non-septate = hyphae without cross wallsnon-septate = hyphae without cross walls Mycelium = complex of hyphaeMycelium = complex of hyphae The term mould is generally used to The term mould is generally used to

describe a fungus which produces hyphae.describe a fungus which produces hyphae. The term yeast is generally used to The term yeast is generally used to

describe a fungus which reproduces by describe a fungus which reproduces by budding.budding.

Morphology:Morphology: Filamentous (mould).Filamentous (mould). YeastYeast DimorphicDimorphic

ReproductionReproduction

--Asexual reproduction--Asexual reproduction Budding, fissionBudding, fission Asexual spore - mitosisAsexual spore - mitosis zoospores, sporangiospores.zoospores, sporangiospores. oospores, zygospores, chlamydosporesoospores, zygospores, chlamydospores

--Sexual reproduction--Sexual reproduction– sexual spore - meiosissexual spore - meiosis– ascospore, basidiosporeascospore, basidiospore

Some fungi have no sexual reproduction Some fungi have no sexual reproduction (Imperfect fungi).(Imperfect fungi).

1- Yeast1- Yeast Round, oval or elongated unicellular cells.Round, oval or elongated unicellular cells. 3-15 µm3-15 µm Few capsulatedFew capsulated ReproductionReproduction

– Sexual .Sexual .– Asexual : by budding (blastoconidia or Asexual : by budding (blastoconidia or

blastospores)blastospores)– May give arise to pseudohyphae May give arise to pseudohyphae

Examples of pathogenic yeast:Examples of pathogenic yeast: Candida albicansCandida albicans

2- Filamentous fungi:2- Filamentous fungi:– MulticellularMulticellular– Form branching filamentous called hyphaeForm branching filamentous called hyphae– Hyphae form myceliumHyphae form mycelium– Hyphae may be septate of aseptateHyphae may be septate of aseptate– Reproduction:Reproduction:– Asexual: by Conidia and sporeAsexual: by Conidia and spore– Sexual. Sexual.

Examples of pathogenic mouldsExamples of pathogenic moulds DermatophytesDermatophytes

3- Dimorphic fungi:3- Dimorphic fungi: Dimorphism Dimorphism this term is used to describe this term is used to describe

a fungus which occurs in two different a fungus which occurs in two different forms (temperature and place), for forms (temperature and place), for example, some pathogenic fungi are example, some pathogenic fungi are filamentous in culture and yeast-like in filamentous in culture and yeast-like in infected tissues.infected tissues.

37°C yeast 37°C yeast 20 – 30° C moulds. 20 – 30° C moulds. Examples:Examples:

– Paracoccidioides brasiliensisParacoccidioides brasiliensis

When fungal infections should be When fungal infections should be considered?considered?

Prolong fever not responding to antibiotics.Prolong fever not responding to antibiotics. NeutropeniaNeutropenia Diabetes with ketoacidosisDiabetes with ketoacidosis Bone marrow and solid organs Bone marrow and solid organs

transplantationtransplantation HIV patientsHIV patients Travel or stay in endemic areas.Travel or stay in endemic areas.

CategoriesCategoriesTrue pathogens – 4 species (dimorphic)True pathogens – 4 species (dimorphic) – – Blastomyces dermatitidisBlastomyces dermatitidis – – Coccidioides immitisCoccidioides immitis – – Histoplasma capsulatumHistoplasma capsulatum – – Paracoccidioides brasiliensisParacoccidioides brasiliensisOpportunistic fungiOpportunistic fungi – – Not cause diseases in healthy Not cause diseases in healthy

individualsindividuals – – Invasive medical proceduresInvasive medical procedures – – Surgery, implantsSurgery, implants – – Medical therapiesMedical therapies

Preexisting conditionPreexisting condition ––inherited defects, AIDS, severe burns, etcinherited defects, AIDS, severe burns, etc

Lifestyle factorsLifestyle factors ––Poor diet, poor hygiene, IV drug abusePoor diet, poor hygiene, IV drug abuse

Mycoses can be classified according to the Mycoses can be classified according to the site of infection into:site of infection into:

1.1. Superficial Superficial

2.2. SubcutaneousSubcutaneous

3.3. Deep (systemic).Deep (systemic).

4.4. Other MycosesOther Mycoses

General notes: General notes: Unlike bacteria colonies, fungal colonies Unlike bacteria colonies, fungal colonies

spread rapidly by the hyphae which spread rapidly by the hyphae which continue to form more and more new continue to form more and more new colonies.colonies.

Rate of growth, color, texture and form of Rate of growth, color, texture and form of the colony is distinct for each species.the colony is distinct for each species.

Is it useful and harmful, some of them may Is it useful and harmful, some of them may be harmful or may even be life-threatening be harmful or may even be life-threatening to humans (e.g. mycotic meningitis), but to humans (e.g. mycotic meningitis), but never cause wide-spread or endemic never cause wide-spread or endemic disease.disease.

Cause complex signsCause complex signs Resistant to antimicrobial agentsResistant to antimicrobial agents Found almost everywhere (spores, fungi)Found almost everywhere (spores, fungi) Inhalation, trauma, or ingestionInhalation, trauma, or ingestion

Spore formation:Spore formation: Most fungi reproduce by forming spores. Most fungi reproduce by forming spores.

When the spores germinate, they send out When the spores germinate, they send out tube-like projections, called germ tubes, tube-like projections, called germ tubes, which lead to the formation of branching which lead to the formation of branching tube-like structures, called hyphae. . The tube-like structures, called hyphae. . The spores may be produced in many different spores may be produced in many different ways and their size, shape, colour, and ways and their size, shape, colour, and manner of production are of value in manner of production are of value in identifying individual species.identifying individual species.

The principle types of spore are as follow: The principle types of spore are as follow:

1-Chlamydospore: a rest stage, forms when a cell 1-Chlamydospore: a rest stage, forms when a cell swells up and develops a thick resistant wall.swells up and develops a thick resistant wall.

2- Arthrospore: a spore forms by septation 2- Arthrospore: a spore forms by septation followed by fragmentation of hyphae.followed by fragmentation of hyphae.

3- Blastospore: a single vegetative cell of yeast 3- Blastospore: a single vegetative cell of yeast which is produced by budding.which is produced by budding.

4- Conidium: a spore produced externally on 4- Conidium: a spore produced externally on a specialized hypae called conidiophore, a specialized hypae called conidiophore, the conidium (plural conidia) becomes the conidium (plural conidia) becomes detached when it mature.detached when it mature.

5- Sporangiospore: a spore produced within 5- Sporangiospore: a spore produced within a swollen spherical cell (sporangium) at a swollen spherical cell (sporangium) at the end of specialized hyphae called a the end of specialized hyphae called a sporangiophore.sporangiophore.